This invention relates to fault detection apparatus for a motor driver interface circuit. Such an interface circuit is disclosed which connects motor power drive apparatus to a computer control and allows motor operation in a plurality of selectable modes, including bang-bang and PWM operation for reversible motors connected in an H-bridge configuration and solenoid mode for a single solenoid device. In each of these modes the interface circuit may be enabled for motor or solenoid activation or not so enabled. It is desired to include fault detection circuitry which monitors the motor or solenoid for shorts to supply or ground voltage while the interface circuit is enabled or not enabled, for shorted load when the interface circuit is enabled and for open load when the interface circuit is not enabled. However, the motor voltage and current conditions for normal and shorted conditions may be different under enabled and not enabled conditions.